Logging into an rb2011uias-2hnd with winbox.exe version 3.11. One computer running Windows 10 logs in with no problem. The Windows 7 Pro computer gets an invalid username / password error, even when the password is copied and pasted from the same file.
Verify that there are not restrictions on the IP addresses that can access the login account. I just verified that one with one of my RB-750 routers. I have a backup admin account that has a very restrictive list of IP addresses that are allowed to use that account. I tried to log on from a different IP and it failed. The error message states: ERROR: wrong username or password